Effects of minerals on the transformation of organic matter during simulated fire-induced pyrolysis

The effect of Fe(OH)(3), Al(OH)(3), birnessite, montmorillonite, and sea sand on changes in the composition of organic matter during heating was investigated. CO2 was released in all treatments, although the experiments were conducted in the absence of oxygen. In the presence of Fe(OH)3, Al(OH)(3), and birnessite, more CO2 was evolved than in the other treatments. Birnessite and Fe(OH)3 enhance the thermal decomposition of polysaccharides and lignin more than Al(OH)(3). Changes in the lignin signature resembled the alterations during aerobic litter decomposition and humification in humus profiles. DRIFT spectra indicate that the formation of aromatic compounds was favoured, especially in the presence of birnessite. (C) 1997 Elsevier Science Ltd.